This is a tracking issue for decommission pre-flight checks, relating to #70486.

Design

• Create initial design doc
• Create test plan
• Create initial tests

Implementation

• Create & implement new request APIs: kv: implement decommission pre-check api #91568
• Implement replica / span config lookup & evaluation: kv: method to check decommission by valid replica replacement availability #91571
• Implement support for allocator dry run: kv: implement allocator support for evaluating decommission viability #91570
• Collect and summarize errors/traces
• Implement CLI flags: cli: implement CLI flags for decommission pre-check #91893

Jira issue: CRDB-20923

Epic: CRDB-20924